This invention relates to a manufactured aggregate derived from the solid oxidation product of an asphaltic material and, more particularly, to a manufactured aggregate for use in the preparation of hot mix asphalt and related bituminous pavements.
Coal fly ash is a waste material generated in large quantities at coal burning power plants. Considerable effort has been made to find an alternative to disposing this material. Various technologies have been developed as a result. For instance, coal fly ash can be treated to form a variety of structural products. Refer to U.S. Pat. No. 5,342,442 and the references cited therein which relate to the use of sewage sludge and coal fly ash in the formation of light weight aggregates.
However, initial studies indicate that coal burning facilities can be converted to utilize naturally occurring asphalts as an alternative energy source. The solid oxidation products resulting therefrom are compositionally and chemically distinct from the various coal fly ash materials previously generated. As a result, such oxidation products have neither been used nor considered in the formulation of structurally useful materials. Coal fly ash typically contains SiO.sub.2, Al.sub.2 O.sub.3 and Fe.sub.2 O.sub.3. Coal fly ash is not typically water soluble. The oxidation products employed herein contain essentially no detectable levels of the above compounds normally found in coal fly ash. Furthermore the oxidation products used in this invention are composed 55% or more of magnesium sulfate, which is highly soluble in water.
It is generally desirable to provide an inexpensive aggregate material, particularly one which is manufactured thereby providing the opportunity to tailor properties, for use in conjunction with a bituminous pavement surface, especially one having enhanced performance properties.
Various features and advantages of the present invention will be apparent from this summary and included descriptions of preferred embodiments, and will be readily apparent to those skilled in the art having knowledge of manufactured aggregate materials, as can be used in the construction of bituminous pavements, roadways, and related surfaces. Such objects, features, benefits and advantages will be apparent from the above as taken in conjunction with the accompanying examples, tables, data and all reasonable inferences to be drawn therefrom.